Condenser pressure control means



March 10, 1970 J. P. NORTON CONDENSER PRESSURE CONTROL MEANS Original Filed Nov. 8, 1966 2 Sheets-Sheet 1 m EMHV INVENTOR. I JO/m Norton MW March 10, 1970 J. P, NORTON I 3,499,293

, CONDENSER PRESSURE CONTROL MEANS Original Filed Nov. 8, 1966 2 Sheets-Sheet 2 COMPRESSOR DISCHARGE PRESSURE PSIG- CONDENSER ENTERING AIR TEMPERATURE "F H92 5 I INVENTOR.

John 2 Norton United States Patent 3,499,298 CONDENSER PRESSURE CONTROL MEANS John P. Norton, St. Louis, Mo., assignor to American Air Filter Company, Inc., Louisville, Ky., a corporation of Delaware Original application Nov. 8, 1966, Ser. No. 592,914. Divided and this application Apr. 8, 1968, Ser. No.

Int. Cl. F25!) 41/00 US. Cl. 62174 2 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to heat exchange circuits where an expandable-condensible working fluid is circulated through a closed heat exchange fluid flow circuit which includes means to vaporize the fluid and condenser means to condense a portion of the vaporized Working fluid, and, more particularly, relates to method and apparatus for advantageously and selectively distributing a noncondensible gas through such circuits in response to the condition of the circulating working fluid to regulate the operation and control the pressure within such circuits.

BACKGROUND OF THE INVENTION This is a division of U.S. application Ser. No. 592,914, filed Nov. 8, 1966.

In a closed circulating fluid, heat exchange circuit, for example a refrigeration circuit, where a vaporizable-condensible working fluid is circulated through the closed circuit and heat is removed from the working fluid in a cooperative condenser, the pressure in the circuit is affected by the vapor pressure of the fluid and, therefore, is a function of the temperature of the working fluid. Many common working fluids, for example refrigerants circulated in refrigeration circuits, have subatmospheric vapor pressures at low temperatures and if a portion of the circuits, for example the condensers, are exposed to ambient air at such extremely low temperatures, subatmospheric pressure can occur within at least a part of the refrigeration circuit. Subatmospheric pressures are undesirable, particularly in nonoperatiug refrigeration circuits, because Subatmospheric pressure promotes introduction of air into the circuit through loose fitting, inactive rotary seals or leaks in various other elements of the circuit. In such circuits even a very small air leak is undesirable because the oxygen and water vapor carried by the air lead to degradation of the refrigerant, or the working fluid, and the products of degradation promote corrosion of the equipment. Furthermore, noncondensible gases which are drawn into the circuit under subatmospheric pressure adversely affect the operation of the circuit and, furthermore, previous circuits have not provided means to accommodate gases, such as air, which are noncondensible relative to the working fluid. Moreover, in previous circuits, particularly refrigeration circuits, it has been necessary to purge such noncondensible gases with a resulting loss of valuable working fluid. In addition, noncondensible gases which have leaked into previous working fluid circulating circuits, such as refrigeration circuits, collect in the working fluid condensing means with resulting loss of working fluid condensing area and condenser eflectivity.

To prevent the inleakage of air, and minimize other adverse eflects of subatrnospheric pressure in refrigeration circuits, it has been necessary to include both pressure and vacuum seals for the rotary elements of the apparatus used to pump or compress working fluid. The pressure seals have been necessary to prevent loss of working fluid when the circuit is in operation under pressure and vac- "ice uum seals are necessary to reduce inleakage of air when the circuit is operating, or is idle, and the refrigerant pressure is subatmospheric in at least a part of the circuit. Such double seal arrangements are complicated, expensive, require considerable maintenance and are only moderately successful.

Various methods have been used to maintain the pressure of the working fluid within selected limits during operation of refrigeration circuits. Such methods have generally been directed to maintaining the temperature and pressure of the refrigerant and have included complicated, expensive, means to regulate the eifective condensing area of the condensers to control heat lost by the Working fluid in accordance with the condition of the refrigerant. Such methods have been moderately successful in controlling the working fluid pressure when the circuits are operating but have no effect when the circuits are not operating.

Additionally, operation of previous refrigeration circuit condensers at low temperature has undesirably decreased the refrigerant pressure at the condenser outlet to decrease the flow rate of the refrigerant supplied to the expansion device and reduce the cooling capacity of the refrigeration circuit.

In accordance with the present invention a novel, straightforward method and apparatus is provided to provide a selected minimum pressure at low temperature within a flow circuit including means for circulating a vaporizable-compressible working fluid and means to alternately vaporize and condense the working fluid. In accordance with the present invention it is recognized that the reliable method and inexpensive apparatus provides means to advantageously distribute noncondensible gases through such a circuit to simultaneously control the pressure and operating characteristics of the circuit and that operating reliability of the circuit is improved because the novel arrangement in accordance with the present invention requires no moving parts.

Moreover, in accordance with the present invention it has been recognized that the advantageous method and apparatus provides means to simultaneously regulate the circuit pressure and the eflective condensing area of the condenser when the circuit is operating and assure a minimum pressure when the circuit is not in operation.

It has been further recognized that the advantageous method and apparatus can likewise be adapted for use in a portable heater wherein a heated partially vaporized Working fluid is circulated through condenser means to heat a stream of air passing through the condenser and condense a part of the working fluid. The method and apparatus in accordance with the present invention improves the operating characteristics of such circuits and assures above-atmospheric pressure within the circuits at all times, even when the circuits are not operating and are exposed to ambient air of very low temperatures.

Various other features of the present invention will become obvious to those skilled in the art upon reading the disclosure set forth hereinafter.

More particularly, in an arrangement where a vaporizable-condensible working fluid is circulated through a cooperatively interconnected circuit including pump means to pump the fluid, means to vaporize the fluid, and condenser means to condense a portion of the fluid, the present invention provides a method for controlling operation of the circuit including: introducing a noncondensible gas into the circuit in response to decrease in vapor pressure of the working fluid circulated through the circuit so the total gas pressure of the circuit is in excess of the vapor pressure of the working fluid; and, removing a portion of the noncondensible gas from the circuit in response to an increase in vapor pressure of the working fluid.

In accordance with the present invention a novel interconnected fluid flow circuit also is provided including: pump means to circulate vaporizable-compressible Working fluid through the circuit; condenser means to receive working fluid to condense a vaporized portion of such working fluid; gas supply means to supply noncondensible gas having a vapor pressure substantially greater than the vapor pressure of the working fluid; means to cooperatively, communicatively, connect the gas supply means into the circuit so the noncondensible gas is supplied to the circuit in response to decreased vapor pressure of the working fluid to increase the total pressure of the circuit; means to remove noncondensible gas from the circuit in response to increase in equilibrium pressure of the working fluid to return the noncondensible gas to the gas supply means; and, means to pass a fluid to be heated through the condenser means in heat exchange relation with cooling medium to remove heat from the vaporizable-condensible working fluid.

It will be realized by those skilled in the art that various changes can be made in the arrangement, form, or configuration of the apparatus and method disclosed herein without departing from the scope or spirit of the present invention.

Referring now to the drawings:

FIGURE 1 is a schematic representation of a refrigeration circuit including a control arrangement in accordance with the present invention;

FIGURE 2 is a schematic representation of a portable heater arrangement including a control arrangement in accordance with the present invention; and,

FIGURE 3 is a diagram illustrating the effect of a control arrangement in accordance with the present invention.

FIGURE 1 is an illustration of a novel refrigeration circuit including a pump or compressor 1 connected to a refrigerant condenser 2 by means of conduit 3. A fan means 5 can be provided to supply cooling medium, for example air, to condenser 2 and a receiver 4 can be provided to receive compressed, cooler, refrigerant emitted from condenser 2. Compressed, cooled refrigerant can be supplied through conduit 6 to an expansion device 7, for example a thermostatic expansion valve. Expanded refrigerant emitted from expansion valve 7 is supplied to evaporator 8 to provide cooling effect to space 9 to be conditioned, and the expanded refrigerant is returned to compressor 1 by means of conduit 13.

As shown in the example of FIGURE 1, a nonconiensible gas storage chamber 12, in accordance with the present invention, is provided and can be connected to :he top, or gas holding portion, of receiver 4 by means of conduit 14. Conduit 14 can include a valve 11 to regulate flow of gas from chamber 12 to receiver 4 and valve 11 can be completely closed to prevent the flow at gas from chamber 12 to receiver 4, particularly when gas is being charged to chamber 12.

Chamber 12 is advantageously disposed, in relation to :ondenser 2, so that the noncondensible gas migrates to :hamber 12 upon an increase in the temperature of the v orking fluid accompanied by a corresponding increase n the vapor pressure of the working fluid. Furthermore, :hamber 12 can advantageously be disposed so working Fluid or refrigerant which condenses in chamber 12 is returned to the refrigeration circuit by gravity flow.

As shown in the example of FIGURE 1 the desired affect can be achieved, for example, by attaching a single ipe connection 14 from chamber 12 to the top section )f refrigerant receiver 4. Also, a second connection, for :xample conduit 15 including a valve 16, can be pro- Iided to connect the top of condenser 2 with chamber [2 to provide an escape for noncondensible gas which :an collect adjacent the top of condenser 2. An alterna- .ive embodiment (not shown) which can, for example, Je used in refrigeration systems where the receiver has .imited capacity or is frequently removed from the circuit includes a noncondensible gas storage chamber disposed above the condenser and connected to the top of the condenser so refrigerant migrating to the gas storage vessel is condensed to flow by gravity through a conduit to the condenser while the noncondensible gas is removed directly from the top of the condenser.

In operation of the example of a refrigeration circuit in accordance with the present invention, as shown in FIGURE 1, storage chamber 12 can be adapted to be charged with a selected gas having a pressure above atmospheric and substantially greater than the partial. pressure of the working fluid so that practically all of the selected gas remains in the gaseous phase to provide a superatmospheric pressure when a substantial amount of the working fluid has condensed to the liquid phase at low temperature. The selected gas which has a relative volatility substantially greater than the relative volatility of the refrigerant and can be considered relatively noncondensible, for example dry nitrogen, is charged to chamber 12 from a high pressure source, above atmospheric pressure, (not shown) and valve 11 which can be a manual valve and is normally open during operation can be closed during the charging operation so that the quantity of gas charged to chamber 12 can be easily computed in accordance with the volume of chamber 12 and the pressure and temperature of the gas in chamber 12. The quantity of gas charged to chamber 12 can be selected to provide a selected effect and can, for example, be the quantity necessary to provide a selected pressure in the circuit at a selected minimum temperature. The quantity would therefore be computed in accordance with the volume of the circuit and the volume of the liquified working fluid at the selected temperature. After chamber 12 has been charged valve 11 is moved to normally open position so gas flows to receiver 4 to mix with the refrigerant vapor in receiver 4 and. condenser 2 where the vapor pressure exerted by the refrigerant is less than the pressure originally exerted by the noncondensible gas charged to chamber 12.

When the circuit is not operating, the relatively noncondensible gas from chamber 12 maintains the pressure in the system in accordance with the temperature of the gas, the equilibrium pressure of the working fluid liquid and the volume occupied by the liquified working fluid.

When the circuit is in operation the refrigerant emitted from compressor tends to concentrate the noncondensible gas in the area of condenser 2, receiver 4, and chamber 12. Noncondensible gas tends to be swept from the condenser by the refrigerant emitted from compressor 1 and the quantity of noncondensible gas retained in condenser 2, is directly affected by the volume occupied by the refrigerant and the flow rate of refrigerant through condenser 2. A bleed line 15 can be provided to connect the top of condenser 2 with chamber 12 to remove the noncondensible gas which collects at the top of condenser 2 and which is not swept from condenser 2 by refrigerant emitted from compressor 1. Bleed line 15 can include a normally open valve 16 to be closed as desired to prevent flow through conduit 15. It will be noted that in the example of the refrigeration apparatus of FIGURE 1 the noncondensible gas will not normally flow from receiver 4 through evaporator 8 to the inlet of compressor 1 so long as there is liquid refrigerant in receiver 4.

In operation when the pressure in condenser 2 is in excess of the pressure necessary to force all of the noncondensible gas into chamber 12, the quantity of noncondensible gas in receiver 4 or condenser 2 is negligible. In accordance with the present invention it has been recognized that when the refrigerant pressure at the discharge of the condenser 2 decreases, in response to decreased refrigerant vapor pressure, noncondensible gas flows from chamber 12 to receiver 4 and into condenser 2 to reduce the effective condensing surface of the condenser. The migration of noncondensible gas to condenser 2 decreases the condensing area and therefore, decreases the rate of condensation of refrigerant in condenser 2 and can increase the temperature and vapor pressure of refrigerant emitted from condenser 2. It has been recognized that the increased pressuer in receiver 4 and condenser 2 resulting fromthe introduction of noncondensible gas in accordance with the present invention advantageously increases the discharge pressure of compressor 1 to stabilize the operation of compressor 1.

It will be noted that by proper selection of the relatively noncondensible gas charged to chamber 12 and the volume of chamber 12 the present invention provides a straightforward, reliable means to" control the discharge pressure of the compressor by directly controlling the pressure within the circuit and simultaneously decreasing the effective condensing area of condenser 2. The decreased condensing area, in turn, decreases the heat loss experienced by the refrigerant in the condenser resulting in an increase in the temperature and vapor pressure of the working fluid.

In the operation of one example of an apparatus in accordance with the present invention, as shown in FIGURE 1, the volume of chamber 12 was approximately 1.5 times as great as the volume of the entire circuit not occupied by liquifie'cl refrigerant. FIGURE 3 illustrates data from an actual comparison of the operation of such a refrigeration circuit, in one case using the method "and apparatus of the present invention and, in another case', the operation of the same refrigeration circuit without the advantageous method and apparatus provided by the present invention. Referring to FIGURE 3 the discharge pressure of the compressor, for example compressor 1 of FIGURE 1, is shown on the vertical axis and the temperature of the air entering the condenser, for example condenser 2 of FIG- URE 1, is shown on the horizontal axis. Curve A represents the chance in discharge pressure with change in entering air temperature as experienced in operation of the circuit without the advantageous method and apparatus in accordance with the present invention. Curves B and C show the change in discharge pressure with change in condenser air temperature experienced when the refrigeration circuit is operated in accordance with the method of the present invention and the slope of lines B and C relative to the slope of line A illustrates the effect of operation in accordance with the method of the present invention.

Specifically, Curve B represents the variation in discharge pressure experienced in the operation of a refrigeration circuit in accordance with the present invention as the temperature of the air supplied to condenser 2 is decreased. A decrease in the temperature of air supplied to the condenser decreases the temperatureof the refrigerant and therefore the refrigerant vapor pressure with a resulting decrease in compressor discharge pressure. Considering Curves A and B of FIGURE 3 it is clear that the introduction of a controlled quantity of noncondensible gas to the circuit in response to decreased working fluid vapor pressuer advantageously provides increased compressor discharge pressure.

Curve C represents the variation in compressor discharge pressure experienced in the operation of a refrigeration circuit in accordance with the present invention as the temperature of the air supplied to the condenser 2 is increased. An increase in the temperature of the air supplied to the condenser increases the temperature of the working fluid and the vapor pressure of therefrigerant. It will be noted that Curve C of FIGURE. 3 approaches Curve A indicating the removal of the relatively noncondensible gas from the system iri response to increasing temperature of the air supplied to condenser 2. At point P Curves A and C cross indicating elimination of all noncondensible gas from the system.

The performance curves show that introduction of a relatively noncondensible gas into the circuit, in accordance with the method of the present invention, desirably provides an increased compressor discharge pressure when the temperature of the cooling medium supplied to the condenser is low and does not adversely affect the operation of the circuit when the temperature of the cooling medium supplied to the condenser is increased so the equilibrium pressure of the refrigerant emitted from the condenser is equal to pressure of the noncondensible gas as originally charged to chamber 12. It is to be noted that when the equilibrium pressure of the refrigerant is equal to the pressure of the relatively noncondensible gas as charged to chamber 12, point F of FIGURE 3, all of the noncondensible gas has been collected in chamber 12 and the circuit operation is unaffected by the presence of the noncondensible gas in chamber 12.

As stated hereinbefore, the method and apparatus in accordance with the present invention can be adapted for use in fluid heating circuits where an expandable-condensible fluid is at least partially vaporized to be circulated through a working fluid condenser means to heat a stream of fluid passed through the condenser in heat exchange relation. FIGURE 2 is one example of such an application in accordance with the present invention where the operation of a portable heater, to heat a stream of air, is improved by providing a selected noncondensible gas on the circuit and regulating the distribution of such noncondensible gas by means in accordance with the present invention.

The heater of FIGURE 2, which in many respects is similar to that disclosed in assignees application Ser. No. 5 16,641 filed Dec. 17, 1965, applicant John P. Norton includes a working fluid generator 31 to provide a vaporized working fluid which can be used to provide power to auxiliary components of the heater and to heat the stream of air to be heated by the heater.

In the example of the heater shown in FIGURE 2, engine 32 receives vaporized motive fluid from generator 31 and transforms a portion of the pressure energy of the motive fluid to rotary motion to drive power transmitting means 34. Reduced pressure motive fluid is exhausted from turbine 32 to condenser 33 and a portion of the vaporized motive fluid from generator 31 is bypassed around engine 32 through bypass 44 to maintain a constant differential pressure across engine 32. Means, for example pressure responsive valve 46, can be provided to control the differential across engine 32 and the pressure at the outlet of generator 31. The working fluid bypassed around engine 32 and the fluid passed through engine 32 are recombined to flow to condenser 33 to impart heat to the fluid passed through the condenser in heat exchange relation. Motive fluid exhausted from condenser 33 passes to receiver 39 to be recycled to generator 31.

In the examples of FIGURE 2 power transmitting device 34 driven by fluid responsive engine 32 drives auxiliary equipment necessary for the operation of the heater. Such auxiliary equipment can include a combustion air blower 45 to provide combustion air to working fluid generator 31, a fan 37 to move the air stream to be heated through condenser 33, and a motive fluid feed pump 38 which pumps working fluid from receiver 39 to generator 31 for revaporization of the motive fluid.

Fuel to be burned in fluid generator 31 can be provided by means of a pump 41 also driven by power transmitting means 34 where the fuel is delivered from a source (not shown). A fuel control valve 42 can be provided to be operated in response to selected conditions, for example the temperature of the air emitted from condenser 33 as measured by thermal element 43. The rate at which fuel is provided to working fluid generator 31 determines the rate of vaporization of working fluid and therefore the quantity of heat provided to condenser 33.

Working fluid emitted from engine 32 is passed to condenser 33 which also receives an air stream in heat exchange relation. Working fluid flows from condenser 33 to receiver 39.

In accordance with one feature of the present invention a noncondensible gas chamber 48 is provided and is 7 :onnected to the upper portion of receiver 39 by means )f conduit 49 including valve 51. Chamber 48 is charged vith superatmospherie noncondensible gas in a manner imilar to the method described for charging chamber [2 of the apparatus of FIGURE 1.

The operation of the apparatus in accordance with the :xample of FIGURE 2 is in some respects similar to the eration of the refrigeration circuit of FIGURE 1 in bat the vapor pressure of the working fluid in the circuit leter mines the amount of noncondensible gas admitted to he circuit. An increase in the vapor pressure of the workng fluid in response to an increase in the temperature of he working fluid causes more noncondensible gas to migrate to chamber 48. On the contrary a decrease in workng fluid temperature accompanied by a decrease in workng fluid vapor pressure increases the amount of non- :ondensible gas in the system and the condenser to de- :rease the effective condensing area and the rate of heat oss to the air stream passing through condenser 33. It s to be noted that the vapor pressure of the working luid in condenser 33 is a direct function of the amount )f heat added to the working fluid in generator 31. In he example of FIGURE 2, as the temperature of the Lil stream is decreased below the desired value the fuel 'eed rate is increased to increase the quantity of working luid vaporized so the pressure of the working fluid in :ondenser 33 is increased to drive more of the nonconlensible gas into chamber 48 and increase the effective neat transfer area to increase the temperature of the air :tream. Conversely, as the temperature of the air stream s increased above the desired value the fuel feed rate is lecreased to decrease the rate of vaporization of working luid so the pressure at the outlet of condenser 31 is dezreased and noncondensible gas blocks a portion of the :ondenser to decrease the effective heat transfer area.

The invention claimed is:

1. In a refrigeration circuit through which a selected aporizable-condensible refrigerant flows, including coop- :ratively related compressor means to compress a refrigarant, condenser means to receive compressed refrigerant 'rom said compressor to condense such compessed refrigrrant, expansion means disposed in said circuit downtream of said condenser means to receive compressed :ondensed refrigerant from said condenser means to reduce the pressure of such compressed refrigerant, evaporator means to receive reduced pressure refrigerant from said expansion means, and means to return such expanded refrigerant to the inlet of said compressor, the present invention provides an improved control system including: gas supply means to store a selected quantity of relatively non-condensible gas of volatility substantially greater than the volatility of said refrigerant; first conduit means communicating with said gas supply means and said circuit between said condenser and said expansions means to supply said gas to said circuit in response to decreased refrigerant vapor pressure in said condenser to maintain superatmospheric pressure in said circuit at selected refrigerant temperature; second conduit means communicating With said condenser and said gas supply means to selectively return fluid, including non-condensible gas, from said condenser to said gas supply means; and means to return said gas from said circuit to said gas supply means in response to increase in Vapor pressure of said refrigerant emitted from said condenser.

:2. The apparatus of claim 1 including condensed refrigerant receiver means cooperatively disposed in said circuit downstream of said" condenser means to receive condensed refrigerantfrom said condenser means wherein said gas supply means is communicatively connected to said receiver means so the pressure of said noncondensible gas is exerted on liquified refrigerant stored in said receiver to restrict flow of gas through said circuit in a downstream direction from said receiver and said gas flows upstream in said circuit from said receiver to said condenser in response to decrease in vapor pressure of said refrigerant.

References Cited UNITED STATES PATENTS 3,064,445 11/1962 Gerten. 3,238,737 3/1966 Shrader 62-149 3,261,174 7/1966 Miner 62-174 MEYER PERLIN, Primary Examiner US. Cl. X.R. 62-196 

